(CN) — Archeologists and those who study prehistory have long assumed that hunter-gatherers, particularly those living in cold parts of the world, ate mostly meat.
But in a new published Wednesday in the peer-reviewed journal "PLOS ONE," researchers argue that hunter-gatherers, at least those living in the Andes mountains of South America, subsisted on a diet composed of roughly 80% plant matter and 20% meat.
Though the study is only of one localized population, its lead author, archaeologist Randy Haas, suspects that the conclusions will apply to other parts of the world.
"There is a distinct possibility that we've gotten the the dietary regime of people in other places wrong in similar ways, for the same reasons," said Haas, an assistant professor at the University of Wyoming
Haas and a team of researchers analyzed the remains of 24 people from the Wilamaya Patjxa and Soro Mik'aya Patjxa burial sites in Peru, near Lake Titicaca, in an area that would later become part of the Inca Empire. The two dozen individuals lived 9,000 to 6,500 years ago.
The researchers used technology that's been around for decades but has recently become a lot more useful to archeologists, called "human bone isotope chemistry," as a way of peering back into time to see what people consumed.
"You are what you eat," said Haas. "And so the things that you put into your body get incorporated into your body tissues, including your skeleton."
Different foods, as it turns out, leave different chemical signatures in the bones — forever. If you eat a lot of meat, your bones will have high levels of nitrogen of a certain isotope (versions of the chemical element with different numbers of neutrons in their nuclei). Fish leaves a different isotope signature, as do two different categories of plants, each leaving their own isotope of carbon.
"You compare to vegetarian to somebody who's on the Paleo diet, you would get very different results," Haas said.
Haas and his team found that early humans living in the Andes subsisted mostly off of wild tubers — plants that grow underground, like potatoes.
"This sort of intensive relationship with wild potatoes seems to have begun 9,000 years ago, rather than like 3,000 years ago," said Haas. "It also suggests that that sort of relationship began almost as soon as people got there," since humans first arrived in Andes around 11,000 years ago.
Archeologists' assumption that early humans' diet was meat-centric was based on two key pieces of evidence: stone tools, including arrowheads you'd find at the end of a spear, and animals bones. Plants don't leave the same kind of trace — that is, until you study bone isotopes.
"We've had, for the longest time, this biased view of the archaeological record," said Haas. "It took this sort of new method to be able to get beyond that."
Haas has uncovered other evidence for a mostly plant-based lifestyle among early humans, including burnt plant remains and "distinct dental-wear patterns on the individuals’ upper incisors," suggesting they consumed a copious amount of tubers.
He added, "I anticipate that when these kinds of analyses are performed elsewhere, because these other places in Europe and North America experienced the same kinds of preservation biases, they're also going to find similar diets."
Should Haas be proved right, it could potentially upend other key assumptions about human development.
"Previously, the narrative was, people move into this region, they're hunter gatherers, foragers, they're there initially hunting large animals," Haas said.
"And then slowly over time, human populations grow, large animal populations decrease, and then people start to devote more of their time and economy to plant foods just of necessity." In other words: meat-eating was natural, ingrained in us, and then we learned to farm. We were forced into eating veggies.
"This really changed that understanding for me," said Haas. "Now, it seems more likely to me that plants played a more prominent role in human diets throughout our species' existence."
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